Reinforcing the origin of volcanic rocks from the Massif Central through the isotopic composition of lead and strontium

Philippe Négrel (1, 2) , C Guerrot (2, 1) , Emmanuelle Petelet-Giraud (2) , Romain Millot (2, 1)

1 ISTO - Institut des Sciences de la Terre d'Orléans - UMR7327
2 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)

The Massif Central in France hosts a large volume of Tertiary to Recent continental alkaline volcanism, with evidence of crustal contamination of the differentiated magmas. Detailed investigations on feldspathic basalts and basanite rocks from the Cantal volcano exposed in the Allanche basin by lead and strontium isotopes reveal i) the role of the mantle components Depleted Mantle (DM) and Low Velocity Component (LVC, corresponding to the European asthenospheric reservoir) end-members based on 208Pb/204Pb and 206Pb/204Pb isotopic ratios, and ii) show contamination by meta-igneous granulites from the lower crust when using 207Pb/204Pb vs. 206Pb/204Pb ratios, as only part of the samples plot along the Northern Hemisphere Reference Line (NHRL) mixing line between DM and HIMU (High U/Pb Mantle) end-members. Cross plotting of Pb-Sr isotopes rules out recycled sediment and/or igneous granulite as potential crustal contaminant for the Cantal basalts, but suggests mixing between the low-velocity component LVC and EMI (Enriched Mantle I)-pelagic sediments. Replaced in the regional context of the Massif Central, we confirm the existence of several mantle sources and different crustal contaminations in the magmas of the Cantal volcano

Mots clés: lead isotopes; French Massif Central volcano; strontium isotopes; basalts

Domaines: Planète et Univers [physics]; Sciences de la Terre; Volcanologie

Philippe Négrel, C Guerrot, Emmanuelle Petelet-Giraud, Romain Millot. Reinforcing the origin of volcanic rocks from the Massif Central through the isotopic composition of lead and strontium. Journal of Geochemical Exploration, 2015, 153, pp.79-87. ⟨10.1016/j.gexplo.2015.03.005⟩. ⟨insu-01138779⟩